Operating device for the movable contact of the main braking gap in an air blast circuit breaker



June 18, 1963 H. FORWALD 3,094,601

OPERATING DEVICE FOR THE MOVABLE CONTACT OF THE MAIN BREAKING GAP IN AN AIR BLAST CIRCUIT BREAKER Filed Sept. 28, 1961 2 Sheets-Sheet 1 INVENTOR. r z qn Q/v 6r A /A/Q June 18, 1963 H. FORWALD 3,094,601

OPERATING DEVICE FOR THE MOVABLE CONTACT OF THE MAIN BREAKING GAP IN AN AIR BLAST CIRCUIT BREAKER Filed Sept. 28, 1961 2 Sheets-Sheet 2 i1 cr -Mi United States Patent 3,094,601 OPERATING DEVICE FOR THE MOVABLE CON- TACT OF THE MAIN BREAKING GAP IN AN AIR BLAST CIRCUIT BREAKER Haakon Forwald, Ludvika, Sweden, assiguor to Allmanna Svenska Elektriska Airtieholaget, Vasteras, Sweden, 21 Swedish corporation Filed Sept. 28, 1961, Ser. No. 141,431 Claims priority, application Sweden Oct. 15, 1960 3 Claims. (Cl. 200-448) My invention relates to air blast circuit breakers, and more specifically relates to a novel pneumatic operating mechanism for operating the blast valve and movable contact of an air blast circuit breaker wherein the movable contact and its cooperating stationary contact are contained within a high pressure air container.

In accordance with the present invention, and for purposes of increasing the opening speed of the movable contact and obtaining better control of the air blast valve, I connect the air blast valve to a first piston and an extension of the movable contact to a second piston. A source of operating pressure is then connected to the space between the air blast valve operating piston and movable contact operating piston which, when exposed to high pressure air, causes these two pistons to move away from one another to open the air blast valve and to assist the opening of the movable contact thereby imparting higher operating speed to the movable contact.

The volume on the opposite side of the blast valve operating piston is then caused to communicate with open air through the cylinder which carries the movable contact operating piston. This channel, however, is cut off after the movable contact operating piston has moved a predetermined distance. Thus, when the movable contact has moved to a predetermined open position, the space on top of the blast valve is closed with respect to external air and is connected to a source of high pressure operating air, whereby the blast valve is quickly reclosed to prevent the 'undue loss of high pressure air in the interrupter chamber.

Accordingly, a primary object of this invention is to provide a novel operating structure for air blast circuit breakers.

Another object of this invention is to provide a novel operating structure for air blast circuit breakers which provides an increase in the operating speed of the movable contact.

A further object of this invention is to provide a novel pneumatic control structure for the blast valve of an air blast circuit breaker.

A further object of this invention is to provide a novel arrangement for the operating structure of air blast circuit breakers whereby the blast valve is reclosed only after the movable contact has reached a predetermined open position.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 shows a portion of the interrupter chamber of an air blast circuit breaker in conjunction with a first embodiment of the novel operating structure.

FIGURE 2 is similar to FIGURE 1 and shows a modification of the operating structure of FIGURE 1 in accordance with the invention.

Referring now to FIGURE 1, I have schematically illustrated, by dotted line 10, the interrupter container which will contain therein sufiicient high pressure air for at least one interruption operation. A portion of the lower wall of chamber is illustrated as wall 11 which is bolted to a movable contact carrying cylinder 12 which carries movable contact 13. The movable con "ice tact 13 cooperates with a stationary contact partially shown as contact 14- which is secured within chamber 11 and is insulated therefrom. By way of example, the contact 14 can be the end of a conductor extending through an insulator bushing which is carried by container 10. The external end of this conductor (not shown) forms one terminal of the device, while housing 10, for example, forms the other terminal of the device.

The movable contact 13 is a tubular member, as illus hated, and has a spider 15 at the lower end thereof to support the arcing contact 16 and receives the upper end of a rod 17.

The container 10 can be placed in communication with open air through the nozle 18 in movable contact 13, internal volume 19 within cylinder 12 and through blast valve 20 when the blast valve is open (the blast valve 20 being shown in its closed position), and thence through outlet channels such as channel 21. The blast valve 20 is secured to a sleeve 21a which is carried by piston 22 which is movable within cylinder 23. The piston 22 is normally biased downwardly by the biasing spring 24. Rod 17 secured to a movable contact 13 extends through sleeve 21a and is axially movable with respect thereto. The lower end of rod '17 is secured to a piston 25 which is movable within the cylinder 26.

The movable contact 13 is normally maintained in the engaged position shown in FIGURE 1 by means of the biasing spring 27 which extends between a shoulder formed in member 12 and the extending flange head at the top of contact 13. The volume 28 which contains spring 24 is seen to communicate with the interior of cylinder 26 and the open air through orifices 31 and 32. The volume 33 which is between the bottom of piston 22 and the top of piston 25 then communicates with a conduit 30 which is connectable to a source of high pressure operating air for operating the device.

In operation and in order to move the contact 13 to a disengaged position, the conduit 30 has a source of high pressure operating air applied thereto. This causes piston 22 to be moved upwardly to thereby open blast valve 20. At the same time, piston 25 begins to move down wardly to cause disengagement between movable contact 13 and stationary contact 14. Since the blast valve 20 is also open, the high pressure air within container 10 will flow at very rapid rate through orifice 13 to play on the are drawn between the movable contact and stationary contact 14, the blast air continuing through open blast valve 20 and out through orifices such as orifice 21.

Because of this flow of air, there is a sharp pressure decrease beneath movable contact 13 so that the movable contact 13 is moved downwardly by the pressure within container 10 and on top of contact 13. Moreover, the operating air pressure from conduit 30 and on top of piston 25 also causes an additional acceleration of the movable contact 13 downwardly toward a disengaged position whereby the operating speed of the movable contact 13 is increased.

During the opening motion of piston 22, it will be observed that the pressure within chamber 28 has been connected to the open air through channel 29 and the lower portion of cylinder 26. Thus, during the opening of the blast valve 20, there is no counter pressure built up against the upper surface of piston 22 whereby the blast valve 20 may be very rapidly operated to its open position. As the movable contact 13 continues to move downwardly, the lower surface 35, which may be a shockabsorbing medium, meets the top of blast valve 21) and begins to move the blast valve 20 toward its closed position.

In order to aid this reclosing of the blast valve and avoid slowing down the movable contact 13 because of the need for the accelerating this additional mass, as the 3 piston 25 moves downwardly it eventually closes the end of channel 29 to close off channel 29 from orifices 31 and 3:2, and thus, the external air. Moreover, the channel 29 will now be connected directly to the conduit 30 where- 'by high pressure air flows through channel 29 and into 'its function of reclosing the blast valve 20 and thus preventing the loss of speed in the movable contact 13'.

Once the lowermost position of the movable contact is achieved, as indicated in dotted lines 36 for piston 25, the movable contact 13 is in its completely open position, and is maintained in this open position by the influence of the high pressure air bearing upon the top of piston 25.

In order to reclose the circuit breaker, the control air conduit 30 is placed in communication with open air by valve means not shown in the drawing. Therefore, the pressure on top of piston 25 is removed and the movable contact 13 may be reclosed by the spring 27.

It is to be noted that during this closing operation and after the piston 25 passes intermediate position 37 shown in dotted lines, the compressed air within chamber 28 will flow into the volume below piston 25 and thus, ac celerate the piston during the last part of its closing motion. Thus, a strong auxiliary closing force is obtained to ensure proper reclosing even if the contacts close on a fault.

FIGURE 2 ilustrates a second embodiment of the invention wherein those components similar to the components of FIGURE 1 are given similar identifying numerals. The structure of FIGURE 2 is provided particularly for relatively high operating current as compared to the operating current to be used in the device of FIG- URE 1.

In FIGURE 2, the piston rod 17 of FIGURE 1 has been replaced by the piston rod formed in two sections, section 38a and 38b, each of which is cylindrical, the interior of rod 38a communicating with chamber 19. The lower rod portion includes a chamber 39 which communicates with channel 40 in rod section 38a. The blast valve has a small orifice 42 therein. In all other respects, the device of FIGURE 2 is similar to that of FIGURE 1.

The space 39 receives a stationary piston 41, as illustrated, which is secured to the bottom of the mechanism as shown. The operation of the device of FIGURE 2 differs from that of FIGURE 1 in that during opening motion of movable contact 13, the air within volume 39 is almost immediately depleted through channel 40 and into volume 19.

During the closing operation, however, a substantial auxiliary closing force will be obtained which corresponds to the pressure of the compressed air on the surface of piston 41. That is to say, with the blast valve 20 in the closed position, there will be high pressure air within the chamber 19 which is applied to the top of piston 41 through channel 40 and volume 39.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof, Many variations and modifications of the principles of my invention Within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1. An operating mechanism for the movable contact of an air blast circuit breaker; said movable contact being movable into and out of engagement with respect to a relatively stationary contact; said movable and stationary contacts being contained within a high pressure air contamer; said high pressure air container having a blast Valve therein for connecting the interior of said container to external atmosphere and causing an air blast past said movable and stationary contacts; said operating mechanism including a piston rod having one end connected to said movable contact; said piston rod extending through said blast valve; the other end of said piston rod being connected to a first piston; said blast valve being connected to a second piston; said first and second pistons having adjacently positioned surfaces defining a first enclosed volume; the opposite surface of said second piston enclosing a second volume whereby application of high pressure gas to said first volume causes operation of said movable contact; and a pressure equalizing channel communicating between said first and second volumes.

2. The device substantially as set forth in claim 1 wherein said first piston is movable into blocking relation with respect to said pressure equalizing channel.

3. The device of claim 2 wherein said piston rod has a channel therein extending into the interior of said container, said channel being closed by a stationary piston.

N 0 references cited. 

1. AN OPERATING MECHANISM FOR THE MOVABLE CONTACT OF AN AIR BLAST CIRCUIT BREAKER; SAID MOVABLE CONTACT BEING MOVABLE INTO AND OUT OF ENGAGEMENT WITH RESPECT TO A RELATIVELY STATIONARY CONTACT; SAID MOVABLE AND STATIONARY CONTACTS BEING CONTAINED WITHIN A HIGH PRESSURE AIR CONTAINER; SAID HIGH PRESSURE AIR CONTAINER HAVING A BLAST VALVE THEREIN FOR CONNECTING THE INTERIOR OF SAID CONTAINER TO EXTERNAL ATMOSPHERE AND CAUSING AN AIR BLAST PAST SAID MOVABLE AND STATIONARY CONTACTS; SAID OPERATING MECHANISM INCLUDING A PISTON ROD HAVING ONE END CONNECTED TO SAID MOVABLE CONTACT; SAID PISTON ROD EXTENDING THROUGH SAID BLAST VALVE; THE OTHER END OF SAID PISTON ROD BEING CONNECTED TO A FIRST PISTON; SAID BLAST VALVE BEING CONNECTED TO A SECOND PISTON; SAID FIRST AND SECOND PISTONS HAVING ADJACENTLY POSITIONED SURFACES DEFINING A FIRST ENCLOSED VOLUME; THE OPPOSITE SURFACE OF 